This invention relates to novel immobilized cells and a culture method utilizing them. More particularly, it relates to immobilized cells prepared by immobilizing microbial cells in a gel carrier and dispersing an absorbent for organic solvents harmful to the cells therein as well as to a method of normally culturing the cells in a medium which already contains harmful organic solvents or to which said solvents are added.
In fermentation industry, the expense of materials to be fermented accounts for a significant part of the total cost so that the more inexpensive materials are the more preferable. However such materials are frequently contaminated with anti-microbial substances harmful to microbial cells. In the case of mass culture in a large tank with the a large amount of water, it is preferable from an economical viewpoint to reuse the post-fermentation culture liquor since a large amount of waste liquor should be treated and a significant part of the constituents of the medium remain therein. However the culture liquor is unavoidably contaminated with various antimicrobial substances including organic solvents used in the process for extracting the culture product from the medium and in crystallizing the same. In addition, it is frequently impossible to treat waste water caused by not only fermentation methods but also various chemical industrial processes, such as activated sludge methods, since the waste water is contaminated with various substances which are harmful to constituent cells contained in the activated sludge.
In the above-mentioned cases, it is necessary to remove these antimicrobial substances to normally culture the cells. Thus we have directed our attention to organic solvents among these antimicrobial substances and have tried to establish a culture method whereby cells can maintain normal vital activity even in the presence of these solvents.
On the other hand, one distinction between the fermentation and other chemical industries is that in the former attention should be paid to the prevention of contamination with infectious microbes when creating pure cultures of a single, microorganism. That is, it is necessary to previously sterilize the medium and apparatus to be employed by, e.g. heating to 120.degree. C. at 1 atm for 10 to 30 min. It is further necessary to give much attention to the prevention of contamination by infectous microbes throughout the culture, which results in additional cost. Furthermore the apparatus itself should stand elevated pressure and temperature levels, and be equipped with a condenser, which brings about enormous expenses in construction and maintenance. Under these circumstances, fermentation without any sterilizing process has been a long-cherished dream of the fermentation industry and considered an "ideal fermentation" method for a long time. In order to realize the ideal fermentation method, we have tried to develop a method for normally culturing particular cells while preventing the growth of infectious cells with substances harmful only to the latter cells.